Either you need to get an affiliate club in Belgium, Croatia, Bulgaria or other club with low (ie 3yrs to get EU citizenship) rules and farm him out for the requisite period or the player must get the needed International caps to qualify. In the interim he can train with your team but cannot play in competitive matches. The only other option I know of would be to use an editor like FMRTE etc and change his nationality by maybe giving him dual nationality, perhaps an EU mother. Of course that would be cheating, but I won't tell if you don't!!!. honest.